Wind Effect Estimation in Side by Side Offloading Operation for FLNG and LNG Carrier Ships

2012 ◽  
Author(s):  
Toshifumi Fujiwara ◽  
Kazuhiro Yukawa ◽  
Hiroshi Sato ◽  
Kazuhisa Otsubo ◽  
Tomoki Taniguchi
Keyword(s):  
Interaction Effect ◽  
Wind Wave ◽  
Estimation Method ◽  
Deep Ocean ◽  
Wind Load ◽  
Shielding Effect ◽  
Wind Effect ◽  
Strong Wind ◽  
Closed Area ◽  
Capability Evaluation

Liquid Natural Gas resource development is often conducted worldwide. Recently the drilling area has gradually expanded from shallow sea area to the deep ocean. A Floating LNG facility (FLNG) and a LNG carrier ship (LNG) are assumed to operate in the open sea expected to wind, wave and current. In this situation, an operational capability evaluation of the LNG would be needed to grasp the operational weather limitation. The effect of each weather element, i.e. wind, wave and current, giving manoeuvring effect to ships, is expected to assess exactly as external loads. In such a situation, wind interaction effect under the operating condition that a FLNG and a LNG are in same closed area is not clearly understood. This paper treats and proposes one estimation method of wind load for the operation of side-by-side offloading including interaction effect of a FLNG and a LNG. The proposed wind load estimation method based on the wind tunnel experiments represents the shielding effect of the LNG behind the FLNG. Operational assessment on ship manoeuvring under strong wind is calculated using the proposed wind load method in the final stage.

scholarly journals Time-Varying Wind Load Identification Based on Minimum-Variance Unbiased Estimation

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Huili Xue ◽  
Kun Lin ◽  
Yin Luo ◽  
Hongjun Liu
Keyword(s):  
Damping Ratio ◽  
Estimation Method ◽  
Minimum Variance ◽  
Wind Load ◽  
Ar Model ◽  
Unbiased Estimation ◽  
Recursive Identification ◽  
Time Varying ◽  
Building Structures ◽  
Shear Building

A minimum-variance unbiased estimation method is developed to identify the time-varying wind load from measured responses. The formula derivation of recursive identification equations is obtained in state space. The new approach can simultaneously estimate the entire wind load and the unknown structural responses only with limited measurement of structural acceleration response. The fluctuating wind speed process is investigated by the autoregressive (AR) model method in time series analysis. The accuracy and feasibility of the inverse approach are numerically investigated by identifying the wind load on a twenty-story shear building structure. The influences of the number and location of accelerometers are examined and discussed. In order to study the stability of the proposed method, the effects of the errors in crucial factors such as natural frequency and damping ratio are discussed through detailed parametric analysis. It can be found from the identification results that the proposed method can identify the wind load from limited measurement of acceleration responses with good accuracy and stability, indicating that it is an effective approach for estimating wind load on building structures.

Probabilistic Fatigue Damage Analysis of Long Span Suspension Bridge Due to Wind Induced Buffeting

2020 ◽  
Vol 980 ◽  
pp. 275-281
Author(s):  
Hu Jun
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Time History ◽  
Suspension Bridge ◽  
Wind Load ◽  
Strong Wind ◽  
Fatigue Reliability ◽  
Long Span ◽  
Fatigue Damage Analysis ◽  
Fluctuating Wind

In order to consider the fluctuating wind load induced fatigue problem of long span suspension bridge, fatigue reliability formula is modified by assuming the fatigue life is accord with the weibull distribution. Based on the accurate bridge buffeting analysis of time history, the stress time history of components of a suspension bridge in east sea China is simulated, and then the fatigue damages and reliabilities are calculated. The results indicate that the main cables and hangers have enough fatigue reliability under the fluctuating wind load, the fatigue failure will not occur; the stiffening girder has larger fatigue damage, under 40 / (m.s-1) mean wind speed action, the girder of mid-support section’s average fatigue life is only 3.103 years, so the girder’s damage under strong wind action should be taken seriously.

scholarly journals Component Combination Rules of Wind Load Effects of Building Structures

2020 ◽  
Vol 10 (24) ◽  
pp. 8775
Author(s):  
Haiwei Guan ◽  
Yuji Tian
Keyword(s):  
Extreme Values ◽  
Simulation Method ◽  
Wind Load ◽  
Combination Method ◽  
Wind Effect ◽  
Building Structures ◽  
Combination Rules ◽  
Load Effect ◽  
Mean Values ◽  
Standard Deviations

Under the action of the same wind azimuth, the extreme values of the wind load effect components of building structures are generated in the along-wind, cross-wind, vertical, and torsional directions. In designing the wind-resistant structure, the extreme values of effect components need to be combined to determine the internal force envelope values of members. Complete quadratic combination (CQC) and Turkstra combination rules are often used to determine the combination value of extreme values of wind effect components. The extreme probability distribution expressions of the CQC, and the Turkstra and approximate rules, are derived. The simplified combination Equations and combination coefficients of the CQC and Turkstra approximate rules are proposed in this paper. We use the combination Equations and Monte Carlo simulation method to analyze the accuracy of Turkstra and its approximate rules. The results show that the combination extreme is associated with the correlation coefficients, mean values, ratios of standard deviations, and fluctuating extremes of effect components. The errors between Turkstra and its approximate rules are small when load effect components show a positive correlation. The errors are largest when the standard deviations of components are equal. Our research results provide a theoretical basis for the combination method of wind load effect components of building structures.

scholarly journals Standardization of Offshore Surface Wind Speeds

2016 ◽  
Vol 55 (5) ◽  
pp. 1107-1121 ◽  
Author(s):  
Y. C. He ◽  
P. W. Chan ◽  
Q. S. Li
Keyword(s):  
Shallow Water ◽  
Surface Wind ◽  
Reference Conditions ◽  
Deep Ocean ◽  
Topographic Effects ◽  
Strong Wind ◽  
Estimation Errors ◽  
Wind Speeds ◽  
Wide Range ◽  
Wind Measurements

AbstractWind measurement offers an essential data source for a wide range of practices in the fields of meteorology and wind engineering. However, records of surface winds are usually influenced by terrain/topographic effects, and direct usage of raw data may bring in nonignorable errors for follow-up applications. A data-driven standardization scheme was recently proposed by the authors to convert the surface wind measurements over rugged terrain into their potential values corresponding to reference conditions, that is, for neutral winds at a height of 10 m above open flat terrain (z0 = 0.03 m). As a complementary part of the preceding work, this study focuses on the standardization of surface wind speeds with marine exposures. The effect of wind strength on the roughness of the sea surface is further taken into account, with emphasis on the difference between deep-ocean and shallow-water cases. As an application example, wind measurements at a buoy site near the coastal line (water depth is 14 m) are adjusted to their potential values, which are then compared with those at a nearby station. The good agreement between the two sets of results demonstrates the accuracy and effectiveness of the standardization method. It is also found that the behavior of roughness length scale over shallow water may differ noticeably from that over deep ocean, especially under strong wind conditions, and an inappropriate usage of marine roughness predictors may result in significant estimation errors.

Application of Computational Fluid Dynamics: Fire Safety Awareness for Gas Station in Dense Urban Areas With Wind Effects

2004 ◽  
Author(s):  
W. K. Chow
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Risk Management ◽  
Fire Safety ◽  
Urban Areas ◽  
Air Flow ◽  
Wind Effect ◽  
Strong Wind ◽  
Gas Stations ◽  
Gas Station

Consequent to a big gas station fire in Macau and another recent one affected by a nearby explosion in a fireworks factory in China, there are concerns on the fire safety issues of gas stations in urban areas. Those two incidents were not too terrible but the situation would be much worse if there was strong wind, especially in a dense urban area where buildings are closely built together. There are many gas stations built within residential areas in Hong Kong. Wind-induced air movement is a transient phenomenon which depends not only on the wind speeds measured at some designated sites, but is also strongly affected by the surrounding environment. For a gas station located adjacent to a taller building, turbulent effects due to incident wind fields would be important. This is not just a safety problem of the gas station, nor for any single building. A risk management system should be worked out by the Authority in the estate district, suburb, or even the whole city. The problem must be considered carefully for cities with dense population and numerous highrise buildings. Computational fluid dynamics (CFD) is a suitable tool for hazard assessment on the spreading of smoke and heat. In this paper, the wind-induced air flow in a gas station fire next to a building was studied by CFD. The CFD simulator selected is the Fire Dynamics Simulator (FDS) version 3.01. Acoustic filtering technique was applied to remove the flow with high Mach number and large-eddy simulations (LES) were applied to model smaller turbulent scales. Different scenarios on the gas station position, building height and distance away from a vertical wall of the building were simulated. Wind effect was simulated by taking the incident air flow as a parabolic boundary layer. The results are very useful for working out risk management in case of accidents. Note that smoke or even flame will spread by following the wind-induced air motion.

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